[A // beginning a pattern (match attribute) is always superfluous --
you're matching "any contentModel element that is a descendant of the
root node" when you may as well match "any contentModel element" since
all elements must be descendants of the root node by definition.]

Jeni,

I want to understand this: is this the behaviour of the key construct?
Will it always do a full recursive traversal of the entire tree to
locate nodes matches by the pattern? Or is there something else that I
need to keep in mind when specifying patterns for keys?